Touch screens can be seen everywhere around us, and touch screens save space to make it easier to be carried about and have better human-computer interaction in the field of personal portable apparatus such as PDAs. Touch screens can be classified into resistive type, capacitive type, surface acoustic wave type, and so on, depending on principles of operation. At present, most commercially available products adopt resistive and capacitive touch screens, especially the latter.
A capacitive touch screen operates with human body's induction by current with the principle of operation as follows. One or two layers of transparent metallic conducting substance are disposed on a surface of a glass substrate as touch electrodes. When a human body touches the touch screen, the capacitance of the touch electrode at the touched spot changes, and according to the change, the position of the touched spot on the touch screen can be detected.
A touch screen using a single layer of transparent metallic conducting substance as touch electrodes is called a surface capacitive touch screen. A touch screen using two layers of transparent metallic conducting substance as touch electrodes is called an inductive capacitive touch screen. As compared with surface capacitive touch screens, inductive capacitive touch screens can penetrate a thicker overlying layer without correction.